Although the world is connected together through the help of cables, the future of this interconnectedness is wireless. Despite wired connections being more reliable and faster, wireless ones still have lots of potential. But how do they even work? Well, radio waves are what wireless connections truly are but in order for radio waves to be sent out there needs to exist a physical component.
This component is a transmitter. Although many people think that's the job of an antenna, they are not wrong but they are also not entirely in the right. You see the transmitter is located in what we call the antenna of a device. Antennas come in all sorts of shapes and the same goes for transmitters. Because of that, there are many different manufacturers of transmitters including Elsema.
Elsema Transmitters
GLR43301
While there are plenty of other Elsema transmitters, the GLR43301 is one that comes with over 4 billion code combinations. This 433 MHz transmitter has a change over relay output that is rated at 8 amps. The GLR43301 is a versatile Elsema transmitter that offers user electable relay output modes.
GLR43301240
Like the GLR43301 the GLR43301240 is a 433 MHz transmitter that has a current consumption of 2.2 mA on standby. Although the GLR43301240 is bigger it is crystal controlled which means it is more reliable. There is also an E version of the GLR43301240 which comes with a weatherproof case.
GLR43302240
With the same relay output rating of 8 amps, the GLR43302240 is a transmitter that has a sensitivity better than 1µV. You get the same standby energy consumption as the GLR43301240 as well as its level of reliability. The difference here is that the GLR43302240 has a 2 channel receiver with relay output instead of 1.
GLR43304240
Something that you will find on this Elsema transmitter that isn't available on the above-mentioned Elsema transmitters is the 4 channel receiver. This type of Elsema receiver comes with a relay output and the GLR43304240 comes with user-selectable relay output modes. All these features as well as the 8 amp relay output rating make the GLR43304240 ideal for crane control, wireless cement truck operation, industrial operation and more.
GLR43303
Although the GLR43303 has a current consumption of 16mA on standby it has a highly sensitive receiver input stage. With the GLR43303 the supply voltage can be DC or AC and the transmitter also has three different latching output modes. These are security latching, regular latching, and momentary mode. You get the same 8 amp rating for the relay output and 433 receiving frequency. The GLR43303 has a 3 channel Elsema receiver.
Types of Wireless Transmitters
AM
Just like you have AM and FM radio there are also AM and FM transmitters. An AM transmitter is one that works on a range of frequencies starting from 540 kHz to 1700 kHz. The IF of an AM transmitter is around 455 kHz. The frequencies in this case are separated by 10 kHz. AM transmitters rely on what is known as AM (amplitude) modulation. This is where the carrier of the information is a high-frequency signal varied by the amplitude of the modulating signal.
FM
An FM transmitter on the other hand is one that has the high-frequency (carrier) signal varied with the amplitude of the modulation signal. This is known as an FM (frequency modulated) output. This is what allows FM transmitters to operate in a frequency range from 88 MHz to 108 MHz. The IF of FM transmitters is about 1.7 MHz.
SSB
With SSB transmitters you have the power of AM and FM transmitters combined into one. The lower sidebands are being transmitted by the AM transmitter whilst the upper band is transmitted by an FM transmitter. When compared to a regular AM transmitter an SSB transmitter is able to save both on power and bandwidth.
Direct Conversion
A direct conversion transmitter works by sending a constellation of signals called QPSK (Quadrature Phase Shift Keying). The set of signals transmitted are I and Q signals which are processed by what are known as DACs. To feed the output of a DAC to another piece of equipment, the data is sent through low pass filtering an architecture that uses an LO (local oscillator).
Super Heterodyne
Utilising the modulated signal coming from a direct conversion transmitter a heterodyne transmitter adds one more mixing component. This is bandpass filtering which is done with the use of one more LO as well as a PA (power amplification) component. The signal goes through all of this before it is transmitted. This is what allows heterodyne transmitters to vary the amplitude of the output signal.
Conclusion
Wireless transmitters may have been in use for a long time, they haven't been as implemented as they are today. The use of these small yet highly important components makes our world a better place, one where we can easily connect with the people we care about. No matter the device that you're using right now there is some level of wireless connectivity that enables you to access the information you need.
